Testing method and test piece of thermal barrier coating

Abstract

A testing method of thermal barrier coating (TBC) is for evaluating the presence or absence of damage to TBC formed on a bending part on which compression stress acts. The method includes a test piece that includes a pair of arm parts, a bending part arranged between the pair of arm parts, and a TBC layer on a bending surface of the bending part; attaching the test piece to a compression testing device after preparing the test piece; and applying compression stress to the test piece in a direction for bringing the pair of arm parts close together after attaching the test piece with the compression testing device. The pair of arm parts are arranged so as to separate from each other from base end portions toward front end portions of the arm parts. The bending part is arranged between the base end portions.

The invention claimed is: 
     
       1. A testing method of a thermal barrier coating (TBC) for evaluating a presence or absence of damage to the TBC formed on a bending part on which compression stress acts, the testing method comprising:
 preparing a test piece that includes a pair of arm parts, a bending part arranged between the pair of arm parts, and the TBC layer on a bending surface of the bending part; 
 attaching the test piece to a compression testing device after preparing the test piece; and 
 applying compression stress to the test piece in a direction for bringing the pair of arm parts close together after attaching the test piece with the compression testing device, 
 wherein the pair of arm parts are arranged so as to separate from each other in a direction from base end portions toward front end portions of the arm parts, 
 wherein the bending part is arranged between the base end portions, 
 wherein preparing the test piece includes forming a pair of round holes passing through the arm parts in a plate thickness direction of the pair of arm parts, 
 wherein attaching the test piece includes attaching the test piece to the compression testing device through pins inserted into the pair of round holes, 
 wherein applying the compression stress includes applying compression stress to the test piece in a direction for bringing the pair of arm parts close together through the pins, and 
 wherein when preparing the test piece, a curvature radius R of the bending part is made within a range of a value of a curvature radius of a second bending part in a real machine to be evaluated, a thickness hc of the TBC layer is made within a range of a value of a thickness of a second TBC layer in the real machine, a thickness hs of the bending part is made within a range of a value of a thickness of the second bending part in the real machine, and a distance H in a lateral direction between a center of the pair of round holes and a center of the curvature radius R is set at a value calculated based on the curvature radius R, the thickness hc, and the thickness hs. 
 
     
     
       2. The testing method of the TBC according to  claim 1 , wherein, when preparing the test piece, the curvature radius R is made within a range from 3 mm or more to 7 mm or less, the thickness hc is made within a range from 0.3 mm or more to 1.5 mm or less, and the thickness hs is made within a range from 3 mm or more to 7 mm or less. 
     
     
       3. The testing method of TBC according to  claim 1 , wherein a central axis of a curvature radius of the bending part extends in a direction perpendicular to a direction in which the compression stress is applied. 
     
     
       4. The testing method of the TBC according to  claim 1 , wherein preparing the test piece includes calculating other dimensions of the test piece based on the calculated distance H, cutting a portion having the calculated dimensions as a main body part out of an ingot to prepare the test piece before the pair of round holes is formed. 
     
     
       5. The testing method of TBC according to  claim 1 , wherein preparing the test piece includes calculating other dimensions of the test piece based on the calculated distance H, cutting a portion having the calculated dimensions as a main body part out of a turbine blade of a gas turbine to prepare the test piece before the pair of round holes is formed. 
     
     
       6. The testing method of TBC according to  claim 5 , wherein the turbine blade to be cut out at preparing the test piece is of the gas turbine before or after operation. 
     
     
       7. The testing method of TBC according to  claim 5 , further comprising calculating a damage limit strain for the test piece cut out of the gas turbine, and determining a quality of the turbine blade based on whether the calculated damage limit strain is within an allowable range. 
     
     
       8. A test piece that is used in a testing method of a thermal barrier coating (TBC) for evaluating a presence or absence of damage to the TBC formed on a bending part on which compression stress acts, the test piece comprising:
 a pair of arm parts; 
 a bending part arranged between the pair of arm parts; and 
 the TBC layer on a bending surface of the bending part, 
 wherein the pair of arm parts are arranged so as to separate from each other in a direction from base end portions toward front end portions of the arm parts, 
 wherein the bending part is arranged between the base end portions, 
 wherein the pair of arm parts has a pair of round holes passing through the pair of arm parts in a plate thickness direction, 
 wherein the test piece is to be attached to a compression testing device through pins inserted into the pair of round holes, 
 wherein a curvature radius R of the bending part is made within a range of a value of a curvature radius of a second bending part in a real machine to be evaluated, 
 wherein a thickness hc of the TBC layer is made within a range of a value of a thickness of a second TBC layer in the real machine, 
 wherein a thickness hs of the bending part is made within a range of a value of a thickness of a second bending part in the real machine, and 
 wherein a distance H in a lateral direction between a center of the pair of round holes and a center of the curvature radius R is set at a value that is calculated based on the curvature radius R, the thickness hc, and the thickness hs. 
 
     
     
       9. The test piece according to  claim 8 , wherein
 the curvature radius R is made within a range from 3 mm to 7 mm, 
 the thickness hc is made within a range from 0.3 mm to 1.5 mm, and 
 the thickness hs is made within a range from 3 mm to 7 mm. 
 
     
     
       10. The test piece according to  claim 8 , wherein a central axis of a curvature radius of the bending part extends in a direction perpendicular to a direction in which the compression stress is applied.